Low noise frontends for LiDAR receiver and methods for controlling the same comprising a multiplexing circuit for selectively connecting each photodetector to a shared amplifier

Abstract

An optical signal detection system includes a plurality of photodetectors configured to detect optical signals reflected from an environment surrounding the optical signal detection system and convert the optical signals into electrical signals. The optical signal detection system also includes an amplifier coupled to the plurality of photodetectors. The amplifier is shared by the plurality of photodetectors and configured to generate an output signal by amplifying an individual electrical signal converted by a corresponding photodetector. The optical signal detection system further includes a multiplexing circuit configured to selectively establish a connection between one of the plurality of photodetectors and the amplifier to amply the electrical signal converted by that photodetector.

The invention claimed is: 
     
       1. An optical signal detection system, comprising:
 a plurality of photodetectors configured to detect optical signals and convert the optical signals into electrical signals; and 
 an amplifier coupled to the plurality of photodetectors via a multiplexing circuit, wherein the multiplexing circuit is configured to selectively establish a connection between one of the plurality of photodetectors and the amplifier to amplify the electrical signal converted by that photodetector,
 wherein each of the plurality of photodetectors is separately coupled to the multiplexing circuit. 
 
 
     
     
       2. The optical signal detection system of  claim 1 , wherein the amplifier comprises a plurality of input branches arranged in parallel, each of the plurality of input branches being coupled to one of the plurality of photodetectors. 
     
     
       3. The optical signal detection system of  claim 1 , wherein the multiplexing circuit comprises a plurality of switches, at least one of the plurality of switches is configured to control the connection between one of the plurality of photodetectors and the amplifier. 
     
     
       4. The optical signal detection system of  claim 3 , wherein the at least one of the plurality of switches is connected in series with an input transistor configured to couple one of the plurality of photodetectors to the amplifier. 
     
     
       5. The optical signal detection system of  claim 2 , wherein the plurality of input branches are connected to a low-impedance node of the amplifier. 
     
     
       6. The optical signal detection system of  claim 5 , wherein the low-impedance node of the amplifier is at a source terminal of an input transistor of the amplifier. 
     
     
       7. The optical signal detection system of  claim 1 , comprising:
 a feedback network comprising a plurality of feedback branches connected in parallel, wherein the multiplexing circuit is further configured to selectively establish the at least one of the plurality of feedback branches for the at least one of the photodetectors when the multiplexing circuit establishes the connection between the at least one of the photodetectors and the amplifier. 
 
     
     
       8. The optical signal detection system of  claim 7 , wherein at least one of the plurality of feedback branches comprising a pair of switches connected in series, wherein an output terminal of the at least one of the photodetectors is connected between the pair of switches. 
     
     
       9. The optical signal detection system of  claim 7 , wherein the at least one of the plurality of feedback branches, when established, is configured to:
 feedback the output signal to the output terminal of the at least one of the photodetectors. 
 
     
     
       10. The optical signal detection system of  claim 1 , wherein the connection between the at least one of the photodetectors and the amplifier is selectively established based on a scanning manner of the optical signal detection system. 
     
     
       11. A method of processing optical signals, comprising:
 detecting, by a plurality of photodetectors, the optical signals; 
 converting, by the plurality of photodetectors, the optical signals into electrical signals; 
 selectively establishing, by a multiplexing circuit, a connection between one of the plurality of photodetectors and an amplifier; and 
 generating, by the amplifier, an output signal by amplifying an individual electrical signal converted by the photodetector establishing the connection with the amplifier,
 wherein each of the plurality of photodetectors is separately coupled to the multiplexing circuit. 
 
 
     
     
       12. The method of  claim 11 , wherein the amplifier comprises a plurality of input branches arranged in parallel, each of the plurality of input branches being coupled to one of the plurality of photodetectors. 
     
     
       13. The method of  claim 11 , further comprising:
 controlling, by a switch of the multiplexing circuit, the connection between one of the plurality of photodetectors and the amplifier. 
 
     
     
       14. The method of  claim 12 , wherein the plurality of input branches are connected to a low-impedance node of the amplifier. 
     
     
       15. The method of  claim 11 , comprising:
 feeding back, by a feedback network, the output signal to an output terminal of the photodetector establishing the connection with the amplifier. 
 
     
     
       16. The method of  claim 15 , comprising:
 filtering, by a resistor-capacitor network of the feedback network, signals generated by at least one of the plurality of photodetectors, the multiplexing circuit, or the amplifier. 
 
     
     
       17. The method of  claim 15 , comprising:
 controlling a gain of the amplifier by applying a portion of the output signal of the amplifier to an input of the amplifier using the feedback network. 
 
     
     
       18. The method of  claim 11 , comprising:
 grounding the output terminal of the photodetector when the multiplexing circuit does not establish the connection between the photodetector and the amplifier. 
 
     
     
       19. A multi-channel operational amplifier circuit, comprising:
 a plurality of input channels configured to receive input signals generated by a plurality of photodetectors; and 
 an amplification unit coupled to the plurality of input channels via a multiplexing circuit, wherein the multiplexing circuit is configured to select one of the plurality of input channels for the amplification unit to amplify the input signal generated by a photodetector received by a corresponding input channel. 
 
     
     
       20. The multi-channel operational amplifier circuit of  claim 19 , wherein the multiplexing circuit comprises a plurality of switches, at least one of the plurality of switches being configured to control the selection of the one of the plurality of input channels.